In capacitively evaluated inertial sensors, especially acceleration sensors having comb structures, signals are transmitted via two contacts (C1, C2) between the evaluation circuit and the sensor element. Via an additional contact (CM), the deflected state of the comb structure is obtained electrically capacitively as a function of the acceleration. For this purpose, the substrate of the sensor element is held to a specified potential using an evaluation circuit, via a fourth contact, substrate contact (CS). If this substrate contact is separated in operation by faulty connecting technique or fatigue, a drifting potential is created as a result of this high-ohmic or open connection. Because of field line shifts and appertaining deflections of the comb structure, conditions in the electrostatic configuration may be reached that correspond to those of an externally applied acceleration, without this actually being the case. In particular, in the case of applications critical to safety, such as ESP, air bag, rollover, ABS and others, this may make fault identification in the electrical connection a requirement.
In the related art, this fault identification, especially the contact-breaking or bond-breaking identification is ensured by an additional contact. By an impressed current over the two contacts, a potential difference may be determined in case of an interruption of a connection that might arise. If the electrical connections are carried out redundantly, the probability that two contacts fulfilling the same function are interrupted is low. However, during the course of further miniaturization of micromechanical sensors, space requirements of contact areas and electrical conducting connections has increasingly become a limiting factor.